The present invention relates to a positioning control apparatus for controlling multi-axis positioning operation by servo mechanisms.
FIG. 4 is a block diagram of a conventional positioning control apparatus in which positioning operation is controlled by a sequence controller. In the drawing, the reference numeral 12 designates a sequencer CPU for performing sequence operations such as a positioning operation procedure or the like, and a positioning control unit 13 for performing positioning control in accordance with a command supplied from the sequencer CPU 12. The positioning controller unit 13 is constituted by a positioning operation part 14 and a servo amplifier interface part 15. A servo amplifier 7 connected with a servo motor 8 is connected to the servo amplifier interface part 15.
The sequencer CPU 12 and the positioning controller unit 13 are unitary formed.
The operation of the positioning control apparatus will be described hereunder. The positioning control unit 13 (hereinafter referred to the positioning unit) is arranged to control the servo motor in accordance with the commands produced from the sequencer CPU 12. The contents of the commands are of positioning target position, start, stop, etc. which are defined by a sequence program. The positioning unit 13 operates acceleration/deceleration processing or the like in the positioning operation part 14 in accordance with the commands, and supplies a control signal to the servo amplifier 7 through the servo amplifier interface part 15 (hereinafter referred to the servo amplifier I/F) in accordance with the results of the operation of the positioning operation part 14. The control signal varies depending on the type of the servo amplifier. For example, in the case of the servo amplifier of the pulse input type, the quantity of movement and the speed are controlled by the number and frequency of pulses respectively, and in the case of the servo amplifier of the analog input type, the speed is controlled by the voltage value.
The servo amplifier 7 drives the servo motor 8 in accordance with these control signals. A position detector (not shown) is provided with the servo motor 8 so that it is possible to perform accurate positioning by a feedback signal supplied from the position detector.
In the conventional positioning control apparatus thus constructed, since the sequencer CPU and the positioning operation part unitary formed are provided for every servo motor unit as described above, the conventional positioning control apparatus is disadvantageous in that when the number of axes for controlling positioning is increased and therefore the number of the servo motors is increased, the devices are required correspondingly, resulting in increase in cost. Further, in the case where the type of the servo amplifier is changed and the state of the control signal is therefore changed, for example, from the pulse input type to the analog input type, servo amplifier interfaces matched to the forms of the control signals are provided or the whole of the apparatus including the positioning operation part is exchanged. This is uneconomical.